1. Field of the Invention
The present invention relates to an optical module, and more particularly to an optical module having a TO-can structure, in which frequency characteristics have been improved in order to achieve high speed transmission.
2. Description of the Related Art
As is generally known in the art, an optical module is an indispensable component for optical communication. The requirements for high speed transmission for the optical module are increased along with the increase of the data transmission volume. Also, it is required to secure an optical broad bandwidth for the frequency adaptable to high speed transmission. At present, a TO-can structure is widely employed as a package for optical devices such as a laser diode and a photo diode in the optical module.
FIG. 1 shows a conventional 10 Gbps TO-can laser module. Such a 10 Gbps TO-can laser module was recently produced by Demeter Technologies Inc. FIG. 2 shows another conventional 10 Gbps TO-can laser module developed by IT Component Division of Sumitomo Electric Industries, Ltd.
Referring to FIG. 1 and FIG. 2, the conventional optical module having a TO-can structure comprises a stem 40 on which a sub-mount 20 is mounted, a laser diode 10 bonded on the sub-mount, a photo diode 30 mounted on the stem 40, a plurality of leads 50 disposed through the stem 40 and electrically connected with the laser diode 10 and the photo diode 30. The sub-mount 20 may be formed from materials such as AIN, SiC, etc., and the stem 40 may be made from materials such as CuW, KOVAR, iron, and etc.
However, such conventional optical modules suffer from parasitic capacitance and inductance due to the use of bonding wires (e.g. connecting the leads and the sub-mount, and connecting the laser diode and the leads). Accordingly, the RF characteristics are deteriorated, resulting in difficulty when the optical modules are used for in high-speed transmission systems covering 10 Gbps. This is because the 3 dB bandwidth is limited within 1 or 2 GHz due to the parasitic components in the package itself.
Further, such conventional optical modules employ a sub-mount designed as a waveguide structure. Therefore, the sub-mount becomes large in size so that the distance between the laser diode and the photo diode becomes longer, bringing about difficulty in achieving adequate monitor photo-current.